Las Vegas, Nevada November 27-30, 2001

Transcription

1 Las Vegas, Nevada November 27-30, 2001 Speaker Name: LeAnne C. Thurmond Project Automation Services Fluor Daniel 100 Fluor Daniel Drive Greenville, SC USA Phone: Fax: Course: BUILDING BLOCKS Using Blocks in AutoCAD GD41-5 (Class, LT, All Levels) Friday, November 30, :30 am to 9:00 am Course Description: Blocks build your AutoCAD drawing. You create blocks to serve as templates to repeat graphical objects. These templates can in turn become AutoCAD drawings. Other drawings can be externally referenced or inserted as blocks. AutoCAD creates unnamed or anonymous blocks for associative dimensions, hatch patterns, images, and layouts. Learn to create intelligent blocks and how to manipulate them to build your drawings faster and better. 1

2 BUILDING BLOCKS Using Blocks in AutoCAD An AutoCAD drawing is made up of graphical and nongraphical objects. The graphical objects (lines, arcs, circles, etc.) are easy to see and understand. The nongraphical information, or named objects, like dimension and text styles, layers, and linetypes, manage the way the graphical objects appear. Named objects are maintained in symbol tables and data dictionaries that can store multiple named object entries. The symbol table of interest here is the BLOCK table. BLOCKS The Block symbol table contains a template of both graphical descriptions and nongraphical information that creates the named object. In other words, the block description includes geometry (lines, arcs, circles, text, attribute definitions, and other block definitions), a base insertion point, and a name. The multiple objects that are grouped together behave as a single object, with a single insertion point. The BLOCK and BMAKE commands create block definitions in the current drawing. The 2000i and 2002 dialog box interface allows you to choose to keep the objects, convert them to a block, or delete them. There is also an option to create a preview icon and description for the AutoCAD Design Center (ADC). At the Command: line, -BLOCK will automatically delete the objects that are selected to become part of the block. To restore the objects, use the OOPS command. Command: -block Enter block name or [?]: HEX Specify insertion base point: 0,0,0 Select objects: A block reference can contain other blocks nested within it. For example, you can insert a drawing of a mechanical assembly that contains a housing, a bracket, and fasteners, with each fastener composed of a bolt, washer, and nut. The only restriction on nested blocks is that they cannot insert or create blocks that reference themselves. 2

3 OBJECT CHARACTERISTICS for BLOCKS Objects that are created on layer 0, with color and linetype BYLAYER, that become part of a block will take on the color, linetype, and visibility characteristics of the layer on which the block is inserted. Objects that are created with color and linetype BYBLOCK that become part of a block will take on the color and linetype characteristics of the layer on which the block is inserted, but will still be controlled by the visibility of the layer on which they are created. Objects that are created on any layer other than 0 that become part of a block will maintain the color and linetype characteristics of the layer on which they were created. Objects assigned object color and/or object linetype will maintain that color and linetype regardless of the layer characteristics. BLOCK NAMES A block name should be as short as possible, but as long as necessary to be descriptive. Prior to AutoCAD 2000, the character limit on the length of internally named objects was 31 characters, any combination of letters, numerals, and the special characters dollar sign ($), hyphen (-), and underscore (_). Xreference names were limited to 8 characters. With AutoCAD 2000i and 2002, the object names can be up to 255 characters long, and include spaces and any special character not used by Windows or AutoCAD for others purposes [such as less-than and greater-than symbols (< >), forward slashes and backslashes (/ \), quotation marks ("), colons (:), semicolons (;), question marks (?), commas (,), asterisks (*), vertical bars ( ), equal signs (=), and backquotes (`)]. If you save an AutoCAD 2000i or 2002 drawing in the format of a previous release, AutoCAD replaces any illegal characters with underscores (_) and shortens the name to 31 characters. AutoCAD preserves the long name and restores it when you open it in AutoCAD 2000i or However, if the name is changed by an earlier AutoCAD version, the long name is lost. To get a list of all blocks in the drawing, enter? in BLOCK on the Command: line Command: -block Enter block name or [?]:? Enter block(s) to list <*>: Defined blocks. "hex" "City base map" Xref: resolved "City base map Arrow" Xdep: "City base map" 3

4 "City base map North Arrow" Xdep: "City base map" User External Dependent Unnamed Blocks References Blocks Blocks User Blocks are those in this drawing s block symbol table. External References are the xref objects. Dependent Blocks are those in the xref objects symbol table. Unnamed Blocks are associative dimensions and other AutoCAD-generated blocks. ATTRIBUTE Attributes are variable text associated with a block definition to store alphanumeric data. The values for the data can be constant (not prompted) or variable (prompted upon insertion). The Attribute Definition object is added as part of the block definition. If the attribute value is variable, the user is prompted for a value to enter into the tag field when the block is inserted. The values of multiple attributes can be edited using the DDATTE command. Attribute data can then be extracted from a drawing using the ATTEXT command or its dialog counterpart and inserted into external files. Attribute characteristics include the tag, prompt, value information, text formatting, location, and any optional modes, like preset or invisible. In 2002 these values can be edited in the Enhanced Attribute Editor dialog box. Using constant attributes in a block allows the text to be moved to a better location without redefining the block. WARNING! Redefinition affects previous as well as future insertions of a block reference. If the block has attached attributes, constant attributes are lost and replaced by any new constant attributes. Variable attributes remain unchanged, even if the new block definition has no attributes. New variable attributes are not added. If you want existing block insertions to use the new attributes, erase the insertions and insert them again. In AutoCAD 2002, the Block Attribute Manager (introduced first in the Express Tools), the Enhanced Attribute Editor, and the Enhanced Attribute Extract dialog box interfaces are BIG enhancements to the usability of attributes, finally getting away from the archaic Command line functions or programming. 4

5 INSERT When a block definition is INSERTed, the graphics are created by reading the template stored in the symbol table. The collection of geometry behaves like a single object. Any change in scaling and rotation will be applied to the Insert object. The scales and rotation can be typed in or specified on-screen. A larger X- than Y- scale will stretch the block along the X axis; the same is true along the other axes. Once a block has been described in a drawing, its name is available on the popdown list. Any drawing can be inserted as a block into any other drawing. The Browse button displays the file dialog box. When another drawing file is inserted, its graphics and symbol tables are written to the block symbol table, then an Insert object is generated to locate the other drawing s graphics. An easy way to insert blocks is drag and drop. Other drawings (*.dwg) can be dragged and dropped from Windows Explorer. The AutoCAD DesignCenter (ADC) allows dragging and dropping of individual blocks from within another drawing. To change the scaling of an insert object from DesignCenter, double click the ADC icon, or right click on the ADC icon of the block and select Insert Block, and enter the desired scale and rotation by typing or by picks. EXPLODE Exploding a block will break it into its constituent parts one level at a time. Nested blocks may need exploded multiple times. The EXPLODE command returns the objects to the layer on which they were created. Using the XPLODE AutoLISP command allows more control over the placement of the objects. If the objects were drawn on layer 0, EXPLODE would place them on layer 0. With XPLODE you can specify which layer the objects will be placed on, as well as their colors and linetypes. Command: xplode Initializing...C:XPlode loaded. Select objects to XPlode. Select objects: Enter an option [All/Color/LAyer/LType/Inherit from parent block/explode] <Explode>: 5

6 Blocks with equal absolute X, Y, and Z scales explode into their component objects (i.e. mirrored blocks now explode). Blocks with unequal X, Y, and Z scales (nonuniformly scaled blocks) might explode into unexpected objects. When a block containing attributes is exploded, the attributes lose their values and revert to the Attribute Definition object. PURGE Exploding a block does not remove its description from the block table. Block descriptions that do not have any inserts that reference them should be PURGEd to remove them from the symbol table. Purging can decrease the size of a file massively. Prior to the wonderful 2000i PURGE dialog box, the Purge command only removes one layer of nesting at a time, so it may need to be issued up to three times. For easy purging in R2000 and R14, create a toolbar button that repeats the command 3 times. In the properties for the button, add the following macro: ^C^C_purge;all;*;n;_purge;all;*;n;_purge;all;*;n [For this to work in R2000i and 2002, replace _ with -.] When inserting an entire drawing into another, selecting the box to Explode on insertion will keep the file size smaller without the need to Purge. WBLOCK An existing block definition, the entire drawing, or selected objects can be written to disk as a separate drawing using the WBLOCK command. When the entire drawing is written out, it is purged of all unused entries in the symbol tables (like unused layers, linetypes, blocks, etc.), which makes it an easy way to purge a drawing completely. When objects are written out, they are not created into a block in the current drawing, and they are deleted. The OOPS command will bring them back as individual objects. 6

7 Command: -wblock Enter name of output file: Enter name of existing block or [= (block=output file)/* (whole drawing)] <define new drawing>: Select objects: XREFERENCES An Xreference is a file whose graphics appear in the current drawing, but whose graphics are not written permanently into the current drawing s symbol table. Any insertions of user-named blocks or unnamed blocks are also temporarily available in the current drawing. The names of these dependent blocks will have the xref name and added as a prefix to the name. Xreferencing is useful in many ways. A single edit to an xreferenced base plan automatically appears in all drawings that reference the base plan next time the xreference is loaded. The referenced graphics are not repeated in all drawings that they appear in, making the file size of the individual drawings smaller and saving disk space. Xrefs may be attached or overlayed. Overlay is usually preferable because it virtually eliminates the problem of circular (self-defining) references. When the XLOADCTL is set to 2 enabled with copy, the xref is demand-loaded from a temporary copy of the drawing file, usually in the \TEMP directory of the system, rather than locking the original file. This is the best setting for a networked environment where many people are working with the project drawings. Xrefs can be made part of the current drawing using the Bind option of the XREF command, which binds the entire drawing, or the XBIND command, which binds the selected portions. When all or part of an xreference is bound, the objects in the xreferenced drawings symbol tables are written to the current drawing with the names changed to reflect the xrefname$0$objectname. This preserves the uniqueness of the symbol table entries for flexibility (such as visibility of layers). The Bind option of the XREF command also has an Insert option, which will merge the xreferences symbol tables into the current one, losing their differentiation. 7

8 UNNAMED BLOCKS AutoCAD itself creates unnamed blocks of its own. Copyclips, associative dimensions, and hatch objects are stored in the same format as user-named blocks, but they are given names by AutoCAD. The names of copyclips that are pasted as blocks begin with A$C*. These should be renamed to something more descriptive if they are not exploded and the definitions purged. Associative dimensions are given the name *Dnn, where nn is an incremental number, increased each time a dimension is created. Hatches are also unnamed blocks that can be exploded into the constituent objects. When a nonuniformly scaled block contains objects that cannot be exploded, they are collected into an anonymous block (named with a "*E" prefix) and referenced with the nonuniform scaling. If all the objects in such a block cannot be exploded, the selected block reference will not be exploded. REDEFINING BLOCKS You can redefine a named block using BLOCK, specifying the name of the existing block and selecting the new objects and insertion base point. You can also update the text description and specify a different icon. When you redefine a block, all the references to that block in the drawing are immediately updated to reflect the new definition. Redefinition affects previous as well as future insertions of a block reference. The graphics of all inserted blocks are updated on the display on the next regeneration of the drawing. If the block being redefined had attached attributes, constant attributes are lost and replaced by any new constant attributes. Variable attributes remain unchanged, even if the new block definition has no attributes or additional attributes. To update the number of variable attributes, the drawing must be reinserted again. In releases prior to 2002, use the Express Tool BATTMAN [Block ATTribute MANager] to synchronize the new attribute definitions with the old attributes. Those attributes that have the same tags will maintain their values. This has been incorporated as a command in

9 To redefine a block within the current drawing Insert the block exploded, make the changes, then redefine the block, using the same name and insertion point. Answer Yes when asked if you want to redefine the block. Wblock the block to a different drawing file. Make and save the changes in the new drawing. Insert the block, using the Browse or File button in the Insert dialog box, or in the Command: line INSERT, enter blockname= to indicate that AutoCAD should read the new definition. Answer Yes when asked if you want to redefine the block. In AutoCAD 2000i and 2002, use the REFEDIT command to do in place editing. IMAGES The Image Manager can attach a raster or bit-mapped image file, combining a variety of formats (including BMP, TIFF, RLE, JPG, PCX, and TGA) with AutoCAD drawings. It functions in much the same way an xreference does, in that the raster object does not reside in the drawing EXPRESS TOOLS For R14, 2000 and 2000i users, the Express Tools include a number of programs that make working with blocks much easier. Many of these appear as enhancements in XLIST to list Xref/Block entities and their properties NCOPY to copy nested objects inside blocks or xrefs to current drawing BTRIM to trim drawing objects to block entities BEXTEND to extend objects to block entities GATTE to edit attributes globally BURST to explode attributes to regular text objects SHP2BLK to convert an externally defined shape into a block ATTOUT and ATTIN to export block attribute values to an external, tab-delimited ASCII file to allow editing, then import them back into the drawing BATTMAN to order and resynchronize attribute definitions within blocks ATTSYNC to resynchronize attribute definitions within redefined blocks BLOCKTOXREF to replace all instances of a standard block with an xref. Also unbinds xrefs that are bound BLOCKREPLACE to globally replace all inserts of one block with another block 9

10 AutoCAD DESIGN CENTER (ADC) The Design Center is a welcome addition to AutoCAD from AutoCAD LT. The Design Center allows you to insert any of the objects from any symbol table in any drawing into the current drawing. This includes xreferences, images, dimensions, hatch patterns, layers anything that exists in the symbol tables and dictionaries of a drawing. The Design Center is an easy way to view and copy blocks between drawings. Please note that if a drawing with the name of the block exists on the AutoCAD Support Path, that drawing will be inserted as the block rather than the one that is viewed within another drawing. 10